For a magnetic disk, which is used as an information record medium in a computer, etc., a requirement of the high recording density is becoming greater in recent years; accordingly films formed on surfaces of the magnetic disk, such as magnetic layers and protective films, are becoming thinner.
In a manufacturing process of the magnetic disk, undercoating layers with non-magnetic metal, undercoating layers with metal, the magnetic layers, the protective films, etc. are formed on surfaces of a disk substrate. Then, in order to remove small protrusions generated during these membrane forming processes and in order to clean up the surfaces of the magnetic disk, the tape cleaning is carried out on the surfaces of the magnetic disk by a polishing apparatus. The tape cleaning is to polish the surfaces of the magnetic disk by pressing tape like abrasives against the surfaces of the magnetic disk while the disk is rotating.
In this tape cleaning process, an air pressure or the spring force as described in the Japanese Patent Laid-Open 1990-106264, for example, was conventionally employed for pressing abrasive tapes against the surfaces of the magnetic disk. In an apparatus employing the spring force as described in the Japanese Patent Laid-Open 1990-106264, for example, a pressure for pressing the abrasive tape against the surface of the magnetic disk was approximately 50-75 g. With regard to the polishing apparatus carrying out the tape cleaning, there are also the Japanese Patent Laid-Open 2001-67655 and the Japanese Patent Laid-Open 2001-71249. The Japanese Patent Laid-Open 2001-67655 has a description of “the pressing force is usually 30-200 g, preferably 50-150 g, more preferably 50-100 g”. The Japanese Patent Laid-Open 2001-71249 has a description of “10 g, for example”.
The thinner the protective film, etc. becomes due to the high recording density, the lower the pressure for pressing the abrasive tape against the surface of the magnetic disk needs to be in order to prevent the damage on the polished protective film, etc. Moreover, a surface position of the magnetic disk moves during a polish due to many factors, such as deformations or waves on the surface of the magnetic disk, a deflection of the surface when the magnetic disk is rotating, assembly alignment errors of the polishing apparatus and a vibration of a spindle that rotates the magnetic disk. In the conventional polishing apparatus employing the air pressure or the spring force, when the surface position of the magnetic disk moves, the pressure for pressing the abrasive tape against the surface of the magnetic disk fluctuates, so that it becomes difficult to polish the surface of the magnetic disk uniformly.
Furthermore, the damage occurs due to the shock when the abrasive tape touches the surface of the magnetic disk, even if the pressure for pressing the abrasive tape against the surface of the magnetic disk is made small in order to prevent the damage on the polished protective film, etc. This is also becoming a problem.